Many devices and systems include various numbers and types of sensors. The varied number and types of sensors are used to perform various monitoring and/or control functions. Advancements in micromachining and other microfabrication techniques and associated processes have enabled manufacture of a wide variety of microelectromechanical (MEM) devices, including various types of sensors. Thus, in recent years, many of the sensors that are used to perform monitoring and/or control functions are implemented using MEM sensors.
One particular type of MEM sensor that is used in various applications is an accelerometer. Typically, a MEM accelerometer includes, among other component parts, a proof mass that is resiliently suspended by one or more suspension springs. If the MEM accelerometer experiences an acceleration, the proof mass moves. The motion of the proof mass may then be converted into an electrical signal having a parameter magnitude (e.g., voltage, current, frequency, etc.) that is proportional to the acceleration.
If a MEM device, such as the above-described MEM accelerometer, experiences a relatively high acceleration, or is exposed to a relatively high force, the proof mass and/or other portions that make up the MEM device can move beyond a desired distance. In some instances, such movement can potentially damage the MEM device; Moreover, the MEM device can exhibit unstable behavior if the proof mass and/or other portions of the MEM device travel too far when a voltage is supplied to the MEM device. Thus, many MEM devices include one or more types of over travel stops or motion limiters that are configured to limit the movement of the proof mass and/or other portions of the MEM device. Such over travel stops include, for example, bumpers formed on the outer perimeter of the proof mass and/or other portions of the MEM device, and/or additional non-device structure.
Although presently-known devices and methods for limiting the travel of MEM device components are generally safe, reliably, and robust, these devices and methods do suffer certain drawbacks. For example, these devices and methods can be fairly complex and costly, and/or can consume an unwanted amount of surface area within the MEM device, and/or can only limit travel in one or two orthogonal axes.
Hence, there is a need for a MEM device, such as an accelerometer, and a method of making the same, that addresses one or more of the above-noted drawbacks. Namely, a device and method that limits over travel in a MEM device and that is less complex and/or costly as compared to present devices and methods, and/or consumes less surface area within the MEM device as compared to present devices and methods, and/or limits travel in at least three orthogonal axes. The present invention addresses one or more of these needs. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.